1. Technical Field
The present invention relates to a laser source device for emitting a laser beam, a projector equipped with the laser source device.
2. Related Art
In recent years, in an opto-electronics field such as optical communications, optical application measurement, or optical displays, laser source devices, which use an oscillation beam from a semiconductor laser source after converting the wavelength thereof, have widely been used. As such a laser source device, there is known a second harmonic wave beam generating device, which is provided with a semiconductor laser source having a mirror structure formed on one end surface and a non-reflecting structure formed on the opposing surface and a non-linear optical member having a mirror structure formed on its light oscillating surface and a non-reflecting structure formed on the opposing surface, and forms a resonator structure between the mirror structures of the semiconductor laser source and the non-linear optical member, thereby generating green light or blue light (see, for example, Japanese Patent No. 3300429(Document 1)).
Further, there is proposed an external resonance laser, which is provided with a semiconductor laser oscillator for emitting a laser beam with a predetermined wavelength and an external resonator for resonating the laser beam emitted from the semiconductor laser oscillator, the external resonator being provided with a photopolymer volume hologram, and the photopolymer volume hologram diffracting the laser beam emitted from the semiconductor laser oscillator and making it enter an optical system inside a resonator, and selectively transmitting the laser beam with a predetermined wavelength and emitting it to the outside in order for stably supplying a laser beam with a narrow wavelength band (see, for example, JP-A-2001-284718 (Document 2)).
However, since in the second harmonic wave beam generating device in the related art as described in the Document 1, the laser beam is not narrow-banded, there remains a problem that the oscillation wavelength of the semiconductor laser source varies in accordance with variation in temperature or that the oscillation wavelength band of the laser beam emitted from the light source is so wide with respect to the allowable band of conversion wavelength of a wavelength conversion element (the same as the non-linear optical member) that an amount of light in the wavelength band in which the wavelength conversion is not performed is large resulting in low conversion efficiency.
On the other hand, the photopolymer volume hologram used for the external resonance laser as described in the Document 2, which is an element composed of a number of interference patterns with different refractive indexes formed in resin in a stacked manner and for narrow-banding the laser beam with the oscillation wavelength and then reflecting it, for example, is an expensive element admitting that it can compose the external resonance laser with a simple configuration. Thus, a problem of increasing the manufacturing cost arises.